Rollers & Sleeves
A good roller setup makes a big difference. It helps the paint go on more evenly, covers the surface quicker, and makes the job feel much less stop-start.
For walls and ceilings, I would use a 9" roller frame with a 9" mid pile sleeve. That is the main setup for bigger flat areas, and it helps you keep a wet edge so the finish looks more even.
For smaller areas, I would switch to a 4" roller and sleeve. They are much easier around shelves, panelling, narrow walls, alcoves, behind radiators, furniture, and awkward little sections where a big roller feels clumsy.
The sleeves are designed for good paint pick-up, low splatter, and a smooth finish on normal interior surfaces. The frames use bamboo handles and recycled metal, so they feel like proper decorating tools while using better materials where possible.
Bigger roller for speed. Smaller roller for control. Both help you get a cleaner finish without making the job harder.